The central hypothesis of this proposal is that several important diseases of the heart manifest by altering the function of the myocardial microvasculature. The investigators plan to use the 17 frame per second cine-CT mode of the Imatron CT scanner to measure the time density curves in the myocardium in several animal models. The major emphasis in this proposal is the mathematical modeling of the shape of the time density curve. The first specific aim of this proposal is to characterize the CT method's ability to quantitate individual microvascular functional components. The investigators will embolize vessels in the heart of selected caliber using microspheres of different diameters ranging from 10 -300 micrometers, in order to impair myocardial performance. The second aim is to evaluate the specificity and sensitivity of the CT-based method for detection and discrimination of disease states in animal models of coronary atherosclerosis. This aim will be studied using three groups of pigs, 28 pigs in each group; (a) hypercholesterolemia-induced pigs, (b) chronic coronary artery stenosis induced by intercoronary stenting and, (c) control subjects. The investigators propose that the contrast for these studies can be injected interveneously, and therefore the technique will be less invasive than intra-arterial coronary angiography.